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As discussed in a previous article (read here), the microGC or microchromatography technique is not new. Yet, its use is still unknown and sometimes it is difficult for some analysts, researchers or chemists to know when and why to use this technique. This article will try to give you some keys.

Analysis of gases and vapors

First of all, the micro GC is dedicated to the analysis of gases and vapors. It is not intended to inject liquids or condensable gases. Indeed, the specific injection technique (micro injector machined in silicon) is particularly adapted to gases, but cannot support liquids which would damage it by obstructing it. When we talk about gas, it can be simple gases like oxygen, carbon dioxide, methane but also more complex gases like HFC, CFC. It can be solvent vapors (methanol, light alcohols, VOCs in general)

The list of compounds that can be analyzed in micro GC is therefore very large. Before validating if this is the technique that suits your needs, here are some notions about micro GC:

  • Simple implementation: to operate your analyzer, you need “carrier” gas, mostly helium, a power outlet and that’s it! The latest model Fusion analyzer integrates the processing software accessible from any terminal. After loading the working method in memory and a few minutes of stabilization, you can start your first analysis: the microGC is equipped with an internal mini-pump and takes only the quantity of gas necessary for its analysis (a few mL).
  • Samples: sample containers can therefore be various: a bag (sampling bag), a gas cylinder, an ampoule, a continuous gas flow, out of a reactor, a vent etc.. It is also possible to inject gas using a syringe and an adapter.
  • MicroGC is a separative technique. Choosing the right column ensures you get an interference-free measurement. As in traditional chromatography, the signal then represents a single molecule.
  • The detector
    Puce du détecteur TCD

    Micro Catharometer Detector (TCD)

    is a micro-catharometer: it is universal (responds to all species), very linear over the 0-100% range and allows to measure in the same analysis very varied concentrations (from 100 ppm to 99% on the same run!)

  • Les analyses are fast: as the injector injects very little gas, the columns are short, the analysis times are on average 2 minutes. And the device can therefore give a result every 2 minutes. On some analyses, it is possible to go even faster.

Limites

Injecteur MEMS de MicroGC

MicroGC MEMS Injector

Regarding condensates, the temperature of your sample is to be taken into account. If it is hot or maintained in temperature (reactor, industrial process, catalysis…) the temperature of the injector must not be lower in order to prevent the condensation of vapors. It can be heated to 100°C. If the sample is at higher temperature, it is possible to cool the gas before introduction, with adapted filtration devices or traps, but it is imperative to validate these devices so that they do not modify the composition of the initial sample that you wish to measure.

In summary, if your sample is gaseous at atmospheric pressure and a temperature of less than 100°C, and does not contain strong acids, then there is a good chance that your analysis is possible in micro GC.

Benefits

In addition to the speed and reliability of the measurement outlined above, micro GC remains a simple technique that can be understood by a variety of non-specialist users. Users of micro GC have above all a need for results and there is no need to be an expert in analysis or chromatography to obtain reliable results.

Micro GCs are small, consume little carrier gas and can be placed closer to your sample.

With the temperature programming of the column, your microGC can be more efficient and simpler than a laboratory GC for any gas analysis.

Exemple d'analyse

Chromatogram on microGC with temperature programming

For any project, in order to validate your application, your sampling (not to be neglected!), do not hesitate to contact us to discuss your current or future project.

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